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VIEW PRODUCTSWhy Balanced Dewatering Matters: A Practical Approach to Reducing Paper Two-Sidedness
Aug 15,2026
Balanced Dewatering: An Important Step Toward Reducing Paper Two-Sidedness
Paper quality begins to take shape long before the web reaches the press section or dryer section. One of the important quality issues established during wet-web formation is paper two-sidedness—the structural and property differences between the wire side and the top side of the finished sheet.
On conventional Fourdrinier paper machines, drainage occurs mainly toward the forming fabric. This one-sided drainage mechanism can create an uneven distribution of fibers, fines and fillers through the thickness of the wet web.
As the sheet continues through pressing, drying and finishing, these initial structural differences may become more noticeable and influence surface properties, printability and dimensional behavior.
For mills facing significant two-sidedness, improving the balance of the forming and dewatering process is therefore an important place to start.
How One-Sided Drainage Creates Different Paper Surfaces
During Fourdrinier forming, water passes downward through the forming fabric.
Some fines and fillers move with the drainage flow toward the wire side, and part of this material can pass through the fabric into the white water system.
At the same time, the developing fiber mat begins to act as a filtration layer. Fines and fillers reaching the upper layers are more readily retained.
The result is an uneven distribution of sheet components between the two sides.
This difference in microscopic structure can later contribute to variations in:
- Smoothness
- Porosity
- Absorbency
- Printability
- Surface strength
- Optical properties
Fiber orientation can further increase the difference.
As fibers become oriented during high-speed forming and one-sided drainage, the resulting structure may respond differently on each side during drying. Unequal shrinkage stresses can then contribute to paper curl.
Moving from One-Sided to Two-Sided Dewatering
A fundamental way to address this problem is to create a more symmetrical forming environment.
Instead of removing most of the water through only one side, two-sided forming technologies allow drainage to take place in both directions.
Gap Former for More Symmetrical Sheet Formation
A Gap Former introduces the stock jet directly between two forming fabrics.
The wet web forms while being supported between these fabrics, allowing water to leave toward both sides of the sheet.
This forming principle reduces dependence on one-directional drainage and creates conditions for a more symmetrical sheet structure.
For paper machines where formation quality and sheet uniformity are important, balanced two-sided drainage can provide a valuable process advantage.
Top-Wire Former as an Upgrade for Existing Fourdrinier Machines
A complete replacement of the forming section is not always necessary.
For an existing Fourdrinier paper machine, installing a Top-Wire Former provides another way to introduce two-sided drainage.
The original bottom forming fabric remains in place while an additional forming fabric is installed above the wet web.
As the sheet travels between the two fabrics, water can be removed from both directions.
According to the source material, this arrangement can help:
- Reduce fiber flocculation
- Improve sheet formation
- Improve through-thickness uniformity
- Reduce paper two-sidedness
This makes the Top-Wire Former a practical option when upgrading an existing Fourdrinier forming section.
Improve Formation Without Rebuilding the Entire Former
When a major forming-section modification is not feasible, the existing Fourdrinier table can still be optimized.
Dandy Roll
Installing a Dandy Roll provides mechanical action on the upper surface of the wet web.
This can improve formation and assist in redistributing fibers and fillers.
The source material refers to research reporting an improvement in formation of approximately 30% under suitable conditions. The actual result will depend on the stock, machine configuration and operating conditions.
Controlled Dewatering Elements
The speed and intensity of early drainage are equally important.
Very aggressive drainage can increase the movement of fines and fillers toward the forming fabric and into the white water.
Using suitable dewatering foils and other controlled dewatering elements can provide a gentler and more progressive drainage profile.
This approach helps the sheet structure develop more gradually and can reduce the difference in component distribution between the two surfaces.
Pressing Should Support, Not Increase, Sheet Asymmetry
Paper two-sidedness cannot be considered only a forming-section issue.
Once the wet web reaches the press section, press configuration continues to influence its structure.
Pressing conditions can affect:
- Surface strength
- Absorbency
- Water removal
- Differences between the two sheet surfaces
Depending on the paper machine configuration, suitable equipment may include:
- Suction Press Rolls
- Blind-Drilled Press Rolls
- Jumbo Press Rolls
The aim is to achieve effective water removal without creating unnecessary differences between the two sides.
For this reason, forming-section and press-section optimization should be considered together.
Calendering Can Further Reduce Surface Differences
After drying, calendering provides an additional opportunity to improve surface uniformity.
Heated calender rolls can improve paper smoothness and help reduce differences between the two surfaces.
Proper operation requires coordinated control of:
- Roll temperature
- Nip pressure
- Sheet moisture
Applying excessive calendering pressure is not necessarily the solution, as it can also influence other sheet properties.
The operating conditions should therefore be selected according to the required final paper characteristics.
Moisture Profiling Helps Address Drying-Related Curl
Not all two-sidedness originates exclusively in the forming section.
Uneven drying can create different stress and strain conditions between the two sides of the sheet.
A Steam Box installed in the dryer or calender area can be used to apply controlled moisture to the paper.
By re-moistening the surface that dries earlier, differences in shrinkage stress can be reduced.
According to the source material, this approach can be particularly useful for addressing curl and two-sidedness associated with certain single-tier dryer configurations.
The Best Solution Begins with Finding Where the Difference Is Created
There is no single machine component that can solve every two-sidedness problem.
The production line should instead be evaluated as a complete system:
Stock Flow → Headbox → Forming → Dewatering → Pressing → Drying → Calendering
If the primary cause is strongly one-sided drainage, downstream surface treatment alone cannot remove the original structural difference.
If drying is contributing significantly to curl, modifying only the forming section may also be insufficient.
Identifying where the asymmetry develops allows the mill to select a more targeted upgrade strategy.
Huatao Group Provides Paper Machine Forming and Dewatering Solutions
Since 2008, Huatao Group has focused on manufacturing and exporting equipment, components and spare parts for the pulp and paper industry.
For paper mills seeking to improve sheet formation, dewatering performance and paper two-sidedness, Huatao Group provides:
- Gap Formers
- Top-Wire Formers
- Dandy Rolls
- Dewatering Elements
- Suction Press Rolls
- Blind-Drilled Press Rolls
- Jumbo Press Rolls
- Calender Rolls
- Bow Rolls
For existing paper machines, equipment selection can be considered according to the machine configuration, paper grade and the specific quality issue being addressed.
If your mill is experiencing poor formation, excessive two-sidedness, uneven surface properties or paper curl, contact Huatao Group for paper machine equipment and upgrade solutions.
Contact Huatao Group
Website: www.huataogroup.com
Email: team3@huataogroup.com
WhatsApp / WeChat: +86 19322109200
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